What are cons to use Cufon? in term of Web Standards, Accessibility and Performance.
I think if we need smooth text than sIFR is still best with screen reader compat
The best solution is to use @font-face. There are already fail-safe solutions for @font-face. sIFR and Cufon:
Look at the Fontsquirrel's font-face generator for a fail-safe solution.
The jagged corners are mostly caused by the operating systems font API. If you really do need to have smooth cornered fonts, instead of relying on js/flash, I'd suggest generating images on server side and with proper alt tags.